The present invention relates to the field of motor vehicle safety and relates more specifically to a protective assembly intended to deploy a protective cushion which serves to block the lower limbs of an occupant of a motor vehicle in an accident.
In order to limit as far as possible the risk of bodily injury run by the occupants of a motor vehicle in the event of a frontal or side impact, the incorporation of gas-generating systems into vehicles so as to inflate protective cushions able to protect the head and thorax of the occupants has been proposed now for about thirty years.
Recently, numerous patent applications have appeared regarding protective assemblies included in the lower part of the dashboard and designed to block the lower limbs of the occupant in a collision so that, on the one hand, said lower limbs are protected and, on the other hand, the occupant cannot slide along the seat in which he is sitting and be injured by the seat belt or, as appropriate, by an inflatable protective cushion.
These various protective assemblies may be classified broadly into three categories. The first category contains protective assemblies which call upon a gas generator mounted fixedly in the lower part of the dashboard and intended to inflate a protective cushion designed to come into direct contact with the occupant""s lower limbs. However, these protective cushions, which are situated near plastic or metal elements, may become damaged by such elements in the event of a collision. Such assemblies are, for example, described in patent application DE 39 34588 and in U.S. Pat. No. 5,458,366.
The second category contains protective assemblies which contain a gas generator intended to inflate a protective cushion which itself actuates a plate designed to come into contact with the occupant""s lower limbs. However, these assemblies, which are described for example in Patent Applications EP 0 684 164 and EP 0 820 905, on the whole have excessively high manufacturing costs and occupy too much space. The third category contains protective assemblies which resort to no inflatable protective cushion. U.S. Pat. No. 5,409,260 and U.S. Pat. No. 4,951,963 for example disclose protective assemblies including a plate which can be moved in the event of an impact so as to meet the occupant""s lower limbs, it being possible for this plate to be actuated pneumatically or mechanically. However, as the maximum deployment of the plate has to be achieved in the ten milliseconds or so following collision, it then follows that said plate is brought up to speed, in the opposite direction to the direction of the lower limbs, extremely sharply during this space of time and that the plate is then likely to injure the occupant""s lower limbs if these strike said plate before it is fully deployed.
The person skilled in the art is therefore still looking for an assembly for protecting the lower limbs of an occupant that makes it possible to alleviate the various problems mentioned previously.
The object of the invention is to meet this expectation and the invention relates to a protective assembly for protecting the lower limbs of an occupant of a motor vehicle, comprising an actuating device secured to the vehicle and able to cause the movement of a sliding means which is connected to a protective system intended to switch from a retracted storage position to a protecting position, characterized in that
i) the actuating device contains a pyrotechnic assembly comprising a pyrotechnic charge with which an ignition device is associated,
ii) the protection system comprises a shock-absorbing protective cushion mounted on a shaft which is secured to the vehicle,
iii) this protective cushion is able to move in rotation under the effect of the movement of the sliding means so as to accompany the movement of said lower limbs in the anticipated area of contact between the lower limbs of the occupant and said protective cushion.
Thus, this protective assembly, which is able to ensure full deployment of the protective cushion in a period of time of the order of 10 milliseconds, allows a great reduction in the risk of injury to the lower limbs when, bearing in mind the particular positioning of the occupant on his seat at the time of the collision, the impact occurs in the instants preceding full deployment of the protective cushion. What actually happens is that, at that moment, this protective cushion is given a movement not in the opposite direction to that of the lower limbs but which accompanies the movement of said lower limbs. In all cases, the effect of the protective cushion is to absorb some of the energy introduced through the impact.
It should be noted that a protective assembly according to the invention may comprise a shaft which can move in rotation under the effect of the movement of the sliding means and to which a protective cushion is fixedly attached. However, one possible alternative form of embodiment may consist in the use of a shaft which is permanently fixed and on which there is mounted a protective cushion that can move in rotation about this shaft under the effect of the movement of the sliding means. The other structural differences to be made to the protective assembly in order to take account of this alternative form of embodiment will not necessarily all be described hereinafter.
Advantageously, the actuating device consists of a linear pyrotechnic tension ram and the sliding means has, on the one hand, a first end connected to a moving part housed in said ram and, on the other hand, a second end connected to the shaft. In the alternative form mentioned earlier, the second end of the sliding means would then be connected to the protective cushion.
It should be noted that, depending on the geometry of the cabin, it may be necessary to use a linear pyrotechnic thrust ram in place of the linear pyrotechnic tension ram.
Bearing in mind the constant increase in the number of protective systems carried on board a vehicle, another object of the invention is to propose a protective assembly that is of small size. For that, the sliding means is advantageously attached to an element that can move in rotation which is connected to the shaft, this moving element preferably consisting of at least one link rod. Hence, by virtue of this moving element, the movement of the sliding means is manifested at the shaft and therefore at the protective cushion by a large-amplitude rotation which causes this cushion to move from a very retracted storage position into a position of maximum protection, this rotation advantageously being through more than 90 degrees.
Advantageously, the actuating device and the moving element are attached to a fixed armature.
According to a first preferred alternative form of the invention, the sliding means consists of a rigid rod and the actuating device is able to rock about a rotation spindle.
According to a second preferred alternative form of the invention, the sliding means consists of a flexible cable.
Advantageously, the actuating device lies in a plane perpendicular to the shaft.
A protective assembly according to the invention may also comprise a braking device which is able to cause a sharp decrease in the speed of the protective cushion at the end of operation. This device then makes it possible to greatly reduce the probability of the protective cushion bouncing back at the end of operation. This braking device may for example be produced using a first metal part which is attached to the actuating device and which acts as a stop for a second metal part mounted on the sliding means. The first metal part is preferably in the shape of a bell and the second metal part preferably consists of a nut secured to the sliding means.
An assembly according to the invention may also contain a blocking device intended to block the protective cushion when it is fully deployed. Several exemplary embodiments of this blocking device will be expanded upon later on in this patent application. This device may incidentally have the effect of supplementing the action of the braking device.
As a preference, the protective cushion is produced in the form of a body having two ends, each of them being fixed to the shaft by means of a fixing lug.
A protective assembly according to the invention, apart from making it possible to very greatly reduce the risk of injury during the impact, and of occupying only a small volume, has the advantage of having only a small number of mechanical parts which are easy to assemble, thus giving this assembly a low cost of manufacture.
The present invention also relates to an actuating device intended to be incorporated into such a protective assembly, characterized in that it comprises:
i) a body in which, during operation, a moving part to which a rod is attached can slide,
ii) a braking device which is able to cause a sharp reduction in the speed of travel of the moving part at the end of operation,
iii) a blocking device intended to block the moving part at the end of operation.
According to a first feature of the invention, said rod may consist of a rigid rod or of a flexible cable.
Advantageously, the braking device is produced using a first metal part which is attached to the body and which acts as a stop for a second metal part mounted on the rod. The first metal part is preferably produced in the form of a bell and the second metal part may consist of a nut. In such an embodiment, as the bell is made to deform under the impact of the nut, it is then possible for said bell and said nut to be configured in such a way that the nut is held captive in the deformed bell. It then follows that, in such a case, the bell and the nut constitute both the braking device and the blocking device.
Furthermore, the blocking device may for example be produced using elastic tabs carried by the side wall of the body, said elastic tabs being intended to close back up, at the end of operation, onto a groove that the moving part has.
This actuating device therefore has the advantage, on the one hand, of having a moving part whose speed of movement is greatly reduced at the end of its travel and, on the other hand, of avoiding any movement of said moving part in the opposite direction at the end of operation.